Thermal Efficiency of Solar Air Heater Having Transverse Rib Roughness Solar Air

Abstract

Conventional (Flat plate) air heaters are found to have low thermal efficiency due to the low convective heat transfer coefficient (h) between the absorber plate and the flowing fluid (air), which leads into higher plate temperature and enhance the thermal losses hence its efficiency is lowered. Use of artificial roughness over the absorber plate of air heater duct is one of the important techniques to achieve this objective. In roughened solar air heaters , rib produces the turbulent in the flow as well as breaking the laminar-sublayer which is present in the flow then heat transfer coefficient increased between air and the absorber plate hence the overall performance of the duct increases as compared to smooth plate solar air heater duct. In the present work thermal and effective (thermohydraulic) efficiency analysis of transverse rib roughened solar air heater has been performed. A mathematical model was developed to compute the performance analytically; the programme codes are developed in MATLAB. Based on the computed results a suitable design or selection of geometrical, operating and flow parameters.